Lake-bed trails tell ancient fish story

Date:

May 6, 2010

Source:

Emory University

Summary:

The wavy lines and squiggles etched into a slab of limestone found near Fossil Butte National Monument are prehistoric fish trails, made by Notogoneus osculus as it fed along a lake bottom, according to experts.

Share:

Total shares:

FULL STORY

Photo of N. osculus body fossil.

Credit: Arvid Aese, U.S. National Park Service.

Photo of N. osculus body fossil.

Credit: Arvid Aese, U.S. National Park Service.

Is it possible to track the movements of an extinct fish in a long-gone lake? It is if you are Emory paleontologist Anthony Martin. He's found that wavy lines and squiggles etched into a slab of limestone found near Fossil Butte National Monument are prehistoric fish trails, made by Notogoneus osculus as it fed along a lake bottom.

He led a detailed analysis, published in PLoS One, that gives new insights into the behavior of the extinct N. osculus, and into the ancient ecology of Wyoming's former Fossil Lake.

"We've got a snapshot of N. osculus interacting with the bottom of a lake that disappeared millions of years ago," Martin says. "It's a fleeting glimpse, but it's an important one."

Fossil Lake, part of a subtropical landscape in the early Eocene Epoch, is now a sagebrush desert in southwestern Wyoming, located in Fossil Butte National Monument and environs. The region is famous for an abundance of exquisitely preserved fossils, especially those of freshwater fish.

Trails left by these fish, however, are relatively rare. The National Park Service had identified about a dozen of them and asked Martin to investigate. Martin specializes in trace fossils, including tracks, trails, burrows and nests made by animals millions of years ago.

One of the fish trace fossils especially intrigued Martin. In addition to apparent fin impressions of two wavy lines, it had squiggles suggesting oval shapes. "The oval impressions stayed roughly in the center of the wavy lines and slightly overlapped one another. I realized that these marks were probably made by the mouth, as the fish fed along the bottom," Martin says.

He then deduced that the trace was likely made by N. osculus -- the only species found in the same rock layer whose fossils show a mouth pointing downward.

Martin brought his detailed notes, photos and sketches of the trace fossil back to Atlanta, where he enlisted the aid of disease ecologist Gonzalo Vazquez-Prokopec and geographer Michael Page, two of his colleagues in Emory's Department of Environmental Studies.

Vazquez-Prokopec, who does digital spatial analyses of geographic patterns of diseases and pathogens, applied similar techniques to the trace fossil data. The results showed a mathematical correlation between the trace impressions and the mouth, tail, pelvic and anal fins of an 18-inch N. osculus.

"This provides the first direct evidence of N. osculus bottom feeding," Martin says. "Not only that, the fish was bottom feeding in the deepest part of the lake. Previous research had suggested that the bottom of the lake had such low levels of oxygen that it was hostile to life. Our analysis indicates that, at least seasonally, some fish were living on the lake bottom."

The scientists were also able to calculate how the fish was moving, and the pitch and yaw of its swimming motion. "The trace fossil lines look simple, but they're not so simple," Martin says, explaining that even the gaps in the lines carry information. "As the British say, 'Mind the gap.'"

"All three of us believe in making scientific data as open and assessable as possible," Martin says, adding that he thinks it may be the first collaboration between a paleontologist, a disease ecologist and a geographer. "This opens up a new technique for studying trace fossils that we hope other people will try and test."

Story Source:

The above post is reprinted from materials provided by Emory University. Note: Materials may be edited for content and length.

July 28, 2015  Scientists write that sea-level rise (3.4 mm/yr) is faster in the Chesapeake Bay region than any other location on the Atlantic coast of North America, and twice the global average (1.7 mm/yr). They ... read more

July 28, 2015  The light-sensing molecules that tell plants whether to germinate, when to flower and which direction to grow to seek more sunlight were inherited millions of years ago from ... read more

July 27, 2015  The Viking hit-and-run raids on monastic communities such as Lindisfarne and Iona were the most infamous result of burgeoning Scandinavian maritime prowess in the closing years of the Eighth ... read more

July 20, 2015  For the first time, advanced technologies made it possible to read parts of a damaged scroll that is at least 1,500 years old, discovered inside the Holy Ark of the synagogue ... read more

July 23, 2015  New research reveals that some of the earliest civilizations in the Middle East and the Fertile Crescent may have been affected by abrupt climate change. These findings show ... read more

July 23, 2015  Measurements of iron speciation in ancient rocks were used to construct the chemistry of ancient oceans. Analysis suggests that it took less oxygen than previously thought to ... read more

July 22, 2015  Animal populations on islands tend to develop weird traits over time, becoming big or small or losing the ability to fly. One less-studied pattern of evolution on islands is ... read more

Feb. 19, 2014  Lake Superior is more than 90 percent iced over, and experts say it may be covered completely before winter's end. Someone has proposed a hike across Lake Michigan, and Lake Huron and Lake Erie ... read more

Apr. 4, 2011  Microscopic remains of dead Phantom midge larvae may explain a few hundred years of history of the living conditions of fish, acidification and fish death in Swedish lakes. Researchers have developed ... read more